How to Back up Cydia & jailbroken apps on iPhone & iPod Touch
What happens if your jailbroken iPhone or iPod Touch gets destroyed? What happens if it merely malfunctions and poof—all of your applications are gone? You're screwed—unless you backed up your apps.
If you want to prevent loss of all your Cydia and jailbroken apps, then you have to back them up—now! To do this, you'll need download and install AptBackup and follow this video guide. It's fairly simple though—if you know how to jailbreak your Apple device, you sure can figure this out.
Just open up AptBackup on your iPhone or iPod Touch, then tap the back button. Open iTunes and sync your device and that's it! The next time you restore or update firmware, you'll have your jailbroken Cydia apps backed up in iTunes.
Warning: Do not restore unless you have to. You will have to jailbreak your device again, as well as download and install AptBackup once more.